This invention relates to a synchronous digital hierarchy switch system and, in particular, one that is suitable for use in the interface between a central office and end user(s) of a public service telephone network (PSTN).
In a conventional switch system which connects the ultimate telephone apparatus to the PSTN central office, each individual switch is connected directly with the other switches constituting the switch system. The number of connections among the switches is thus determined by the following formula:
Number of Connection(s)=n x (nxe2x88x921)/2
where n is the number of switches in the system. It is clearly the case that the larger the number of connections, the higher the probability of failure occurring therein.
In addition, in such conventional switching systems, the linked switches have to configure the path. Otherwise, distinct direct connections must be established. A separate control signal path must also exist.
It is thus an object of the present invention to provide a synchronous digital hierarchy switch system in which the aforesaid shortcomings are mitigated, or at least to provide a useful alternative to the public.
According to the present invention, there is provided a digital switch system for connecting a telephone central office with a plurality of telephone subscriber lines, wherein said system includes at least one central office-digital trunk interface switch member allowing signals to be transmitted between said switch system and said central office, and a plurality of subscriber line interface switch members allowing signals to be transmitted between said switch system and said subscriber lines, wherein each of said subscriber line interface switch members is connected with at least one subscriber line via at least one digital-to-subscriber line converting members, and wherein said central office-digital trunk interface switch member and said subscriber line interface switch members are connected in a ring-shaped structure.